mybatis一對一，一對多，多對多實現方式

1.原始方式

    /**
     * 測試使用QueryVo作爲查詢條件
     */
    @Test
    public void testFindByVo(){
        QueryVo vo = new QueryVo();
        User user = new User();
        user.setUserName("%王%");
        vo.setUser(user);
        //5.執行查詢一個方法
        List<User> users = userDao.findUserByVo(vo);
        for(User u : users){
            System.out.println(u);
        }
    }
}

public class QueryVo {

    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

public class User implements Serializable {

    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private Date userBirthday;
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.dao.IUserDao">

    <!-- 配置 查詢結果的列名和實體類的屬性名的對應關係 -->
    <resultMap id="userMap" type="uSeR">
        <!-- 主鍵字段的對應 -->
        <id property="userId" column="id"></id>
        <!--非主鍵字段的對應-->
        <result property="userName" column="username"></result>
        <result property="userAddress" column="address"></result>
        <result property="userSex" column="sex"></result>
        <result property="userBirthday" column="birthday"></result>
    </resultMap>

    <!-- 根據queryVo的條件查詢用戶 -->
    <select id="findUserByVo" parameterType="com.itheima.domain.QueryVo" resultMap="userMap">
        select * from user where username like #{user.userName}
    </select>
</mapper>

 

---

 

2.一對一，一對多

public class AccountTest {

    private InputStream in;
    private SqlSession sqlSession;
    private IAccountDao accountDao;

    @Before//用於在測試方法執行之前執行
    public void init()throws Exception{
        //1.讀取配置文件，生成字節輸入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.獲取SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.獲取SqlSession對象
        sqlSession = factory.openSession(true);
        //4.獲取dao的代理對象
        accountDao = sqlSession.getMapper(IAccountDao.class);
    }

    @After//用於在測試方法執行之後執行
    public void destroy()throws Exception{
        //提交事務
        // sqlSession.commit();
        //6.釋放資源
        sqlSession.close();
        in.close();
    }

    /**
     * 測試查詢所有
     */
    @Test
    public void testFindAll(){
        List<Account> accounts = accountDao.findAll();
        for(Account account : accounts){
            System.out.println("--------每個account的信息------------");
            System.out.println(account);
            System.out.println(account.getUser());
        }
    }


    /**
     * 測試查詢所有賬戶，同時包含用戶名稱和地址
     */
    @Test
    public void testFindAllAccountUser(){
        List<AccountUser> aus = accountDao.findAllAccount();
        for(AccountUser au : aus){
            System.out.println(au);
        }
    }
}

public class Account implements Serializable {

    private Integer id;
    private Integer uid;
    private Double money;

    //從表實體應該包含一個主表實體的對象引用
    private User user;
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.dao.IAccountDao">

    <!-- 定義封裝account和user的resultMap -->
    <resultMap id="accountUserMap" type="account">
        <id property="id" column="aid"></id>
        <result property="uid" column="uid"></result>
        <result property="money" column="money"></result>
        <!-- 一對一的關係映射：配置封裝user的內容-->
        <association property="user"  javaType="user">
            <id property="id" column="id"></id>
            <result column="username" property="username"></result>
            <result column="address" property="address"></result>
            <result column="sex" property="sex"></result>
            <result column="birthday" property="birthday"></result>
        </association>
    </resultMap>

    <!-- 查詢所有 -->
    <select id="findAll" resultMap="accountUserMap">
        select u.*,a.id as aid,a.uid,a.money from account a , user u where u.id = a.uid;
    </select>

    <!--查詢所有賬戶同時包含用戶名和地址信息-->
    <select id="findAllAccount" resultType="accountuser">
        select a.*,u.username,u.address from account a , user u where u.id = a.uid;
    </select>

</mapper>

 

public class UserTest {

    private InputStream in;
    private SqlSession sqlSession;
    private IUserDao userDao;

    @Before//用於在測試方法執行之前執行
    public void init()throws Exception{
        //1.讀取配置文件，生成字節輸入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.獲取SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.獲取SqlSession對象
        sqlSession = factory.openSession(true);
        //4.獲取dao的代理對象
        userDao = sqlSession.getMapper(IUserDao.class);
    }

    @After//用於在測試方法執行之後執行
    public void destroy()throws Exception{
        //提交事務
        // sqlSession.commit();
        //6.釋放資源
        sqlSession.close();
        in.close();
    }

    /**
     * 測試查詢所有
     */
    @Test
    public void testFindAll(){
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println("-----每個用戶的信息------");
            System.out.println(user);
            System.out.println(user.getAccounts());
        }
    }

}

public class User implements Serializable {

    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    //一對多關係映射：主表實體應該包含從表實體的集合引用
    private List<Account> accounts;
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.dao.IUserDao">

    <!-- 定義User的resultMap-->
    <resultMap id="userAccountMap" type="user">
        <id property="id" column="id"></id>
        <result property="username" column="username"></result>
        <result property="address" column="address"></result>
        <result property="sex" column="sex"></result>
        <result property="birthday" column="birthday"></result>
        <!-- 配置user對象中accounts集合的映射 -->
        <collection property="accounts" ofType="account">
            <id column="aid" property="id"></id>
            <result column="uid" property="uid"></result>
            <result column="money" property="money"></result>
        </collection>
    </resultMap>

    <!-- 查詢所有 -->
    <select id="findAll" resultMap="userAccountMap">
        select u.*,a.id aid,a.uid uid,a.money money from user u left outer join account a on u.id = a.uid
    </select>

    <!-- 根據id查詢用戶 -->
    <select id="findById" parameterType="INT" resultType="user">
        select * from user where id = #{uid}
    </select>

</mapper>

 

---

 

3.多對多

public class UserTest {

    private InputStream in;
    private SqlSession sqlSession;
    private IUserDao userDao;

    @Before//用於在測試方法執行之前執行
    public void init()throws Exception{
        //1.讀取配置文件，生成字節輸入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.獲取SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.獲取SqlSession對象
        sqlSession = factory.openSession(true);
        //4.獲取dao的代理對象
        userDao = sqlSession.getMapper(IUserDao.class);
    }

    @After//用於在測試方法執行之後執行
    public void destroy()throws Exception{
        //提交事務
        // sqlSession.commit();
        //6.釋放資源
        sqlSession.close();
        in.close();
    }

    /**
     * 測試查詢所有
     */
    @Test
    public void testFindAll(){
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println("-----每個用戶的信息------");
            System.out.println(user);
            System.out.println(user.getRoles());
        }
    }

}

public class User implements Serializable {

    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    //多對多的關係映射：一個用戶可以具備多個角色
    private List<Role> roles;
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.dao.IUserDao">

    <!-- 定義User的resultMap-->
    <resultMap id="userMap" type="user">
        <id property="id" column="id"></id>
        <result property="username" column="username"></result>
        <result property="address" column="address"></result>
        <result property="sex" column="sex"></result>
        <result property="birthday" column="birthday"></result>
        <!-- 配置角色集合的映射 -->
        <collection property="roles" ofType="role">
            <id property="roleId" column="rid"></id>
            <result property="roleName" column="role_name"></result>
            <result property="roleDesc" column="role_desc"></result>
        </collection>
    </resultMap>

    <!-- 查詢所有 -->
    <select id="findAll" resultMap="userMap">
        select u.*,r.id as rid,r.role_name,r.role_desc from user u
         left outer join user_role ur  on u.id = ur.uid
         left outer join role r on r.id = ur.rid
    </select>

    <!-- 根據id查詢用戶 -->
    <select id="findById" parameterType="INT" resultType="user">
        select * from user where id = #{uid}
    </select>

</mapper>

public class RoleTest {

    private InputStream in;
    private SqlSession sqlSession;
    private IRoleDao roleDao;

    @Before//用於在測試方法執行之前執行
    public void init()throws Exception{
        //1.讀取配置文件，生成字節輸入流
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.獲取SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.獲取SqlSession對象
        sqlSession = factory.openSession(true);
        //4.獲取dao的代理對象
        roleDao = sqlSession.getMapper(IRoleDao.class);
    }

    @After//用於在測試方法執行之後執行
    public void destroy()throws Exception{
        //提交事務
        // sqlSession.commit();
        //6.釋放資源
        sqlSession.close();
        in.close();
    }

    /**
     * 測試查詢所有
     */
    @Test
    public void testFindAll(){
        List<Role> roles = roleDao.findAll();
        for(Role role : roles){
            System.out.println("---每個角色的信息----");
            System.out.println(role);
            System.out.println(role.getUsers());
        }
    }

}

public class Role implements Serializable {

    private Integer roleId;
    private String roleName;
    private String roleDesc;

    //多對多的關係映射：一個角色可以賦予多個用戶
    private List<User> users;
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.dao.IRoleDao">

    <!--定義role表的ResultMap-->
    <resultMap id="roleMap" type="role">
        <id property="roleId" column="rid"></id>
        <result property="roleName" column="role_name"></result>
        <result property="roleDesc" column="role_desc"></result>
        <collection property="users" ofType="user">
            <id column="id" property="id"></id>
            <result column="username" property="username"></result>
            <result column="address" property="address"></result>
            <result column="sex" property="sex"></result>
            <result column="birthday" property="birthday"></result>
        </collection>
    </resultMap>

    <!--查詢所有-->
    <select id="findAll" resultMap="roleMap">
       select u.*,r.id as rid,r.role_name,r.role_desc from role r
        left outer join user_role ur  on r.id = ur.rid
        left outer join user u on u.id = ur.uid
    </select>
</mapper>